docs: def _compute_imt1100(self, C, sites, rup, dists, get_pga_site=False):
          """
          Computes the PGA on reference (Vs30 = 1100 m/s) rock.
          """
          # Calculates simple site response term assuming all sites 1100 m/s
          fsite = (C['c10'] + (C['k2'] * C['n'])) * log(1100. / C['k1'])
          # Calculates the PGA on rock
          pga1100 = np.exp(self._compute_magnitude_term(C, rup.mag) +
                           self._compute_distance_term(C, rup, dists) +
                           self._compute_style_of_faulting_term(C, rup) +
                           self._compute_hanging_wall_term(C, rup, dists) +
                           self._compute_basin_response_term(C, sites.z2pt5) +
                           fsite)
          # If PGA at the site is needed then remove factor for rock and
          # re-calculate on correct site condition
          if get_pga_site:
              pga_site = np.exp(np.log(pga1100) - fsite)
              fsite = self._compute_shallow_site_response(C, sites, pga1100)
              pga_site = np.exp(np.log(pga_site) + fsite)
          else:
              pga_site = None
          return pga1100, pga_site